Sebastian,

The GetPortals stored procedure which resides at my dev portal after applying your 07.04.00.sqldataprovider script reads as below:

USE [greensky_dnn_db]
GO
/****** Object:  StoredProcedure [dbo].[green_dnn_GetPortals]    Script Date: 20-03-2015 13:44:04 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[green_dnn_GetPortals]
    @CultureCode    nvarchar(50)
AS

SELECT *
FROM   dbo.[green_dnn_vw_Portals]
WHERE CultureCode =
    CASE
        WHEN IsNull(@CultureCode, '') = '' THEN DefaultLanguage
        WHEN @CultureCode = 'en-US' THEN DefaultLanguage
        ELSE @CultureCode
    END
ORDER BY PortalName;

Does it look as it should?

Now you're talkin', man. Bull's eye. :)

Danke shön.